I beg to differ. Especially since the example you gave lean more toward cRPGs, rather than Action games. ARPGs are actually Action games, first and foremost, with the RPG aspect being, well, aspect (or elements in a very simple, basic form). Best examples of ARPGs are obviously Diablo, Titan Quests, Grim Dawn, Torchlight, and to some extent, the Soulsborne series (Demon's Souls, Dark Souls, Bloodborne). In those games I mentioned, infinite leveling ARE fun, and somewhat a must. I haven't played all the games you mentioned, and you most likely mentioned those because they have infinite-leveling, but did you play those games in a grindy fashion? Would you? With a completionist mindset?
I assume those games has choices and consequences, where content would be locked out based on your actions or inactions, so....